In some embodiments, a method includes receiving, at a device, digital audio content to be converted by a digital-to-analog converter to produce analog audio content. The digital audio content has at least one audible frequency. The method also includes selecting, at the device, a first signal and a second signal to output with the analog audio content. The first signal has an inaudible carrier frequency and a bandwidth, and the second signal also has an inaudible carrier frequency and a bandwidth. A difference between the first signal and the second signal is an undesired audible signal. The method further includes outputting, from the device, the analog audio content, the first signal and the second signal, such that when the analog audio content is detected by a recording device the undesired audible signal is detected with the analog audio content.

The present disclosure discloses a signal sending method and device. The method includes: receiving, by a base station, an uplink pilot signal sent by authorized user equipment, and determining a direction vector parameter and a first channel fading parameter of a channel calculating, according to the direction vector parameter and the first channel fading parameter, a first signal beamformer parameter, determining a transmission area of an artificial noise signal according to the direction vector parameter, and calculating a second signal beamformer parameter; and processing a to-be-transmitted signal by using the first signal beamformer parameter and the second signal beamformer parameter, and transmitting the processed signal. In this way, in a non-target direction, energy leakage of the secrecy signal to the authorized user equipment is relatively small, and transmitted artificial noise signals are concentrated in an area with a relatively high secrecy signal leakage risk.

The invention relates to a portable electronic signal generator, and in particular a programmable multi-waveform radiofrequency generator for use as battlefield decoy.

Methods and apparatus to determine a level of inherent jitter for signals from a transmitter and a receiver, and modulate information onto a signal transmitted by the transmitter by using spot jitter (with bandwidth and center frequency modulation) and/or pulse width jitter in a region outside of a data region with inherent jitter to carry communication between systems.

A sequencer for use with an Electronic Warfare system consisting of one or more transmitters and receivers including one or more desired operations; a processor in communication with a memory; the memory storing instructions executed by the processor to sequence the one or more desired operations; an output connected to each of transmitter and receiver devices of the transceiver to control power-up and power-down sequences of the transmitter and receiver devices; wherein the instructions to sequence the one or more operations include instructions to prioritize a high-priority transmit operation such that the high-priority transmit operation is carried out in real-time upon request.

A system is provided that has an ECM (electronic counter measures) system and a transponder monitor connected to or forming part of the ECM system. The system monitors for a transponder signal from a remote transponder. The system determines information, such as transponder location, based on the transponder signal and makes use of the information in the ECM system and/or the system extracts encoded information contained in the transponder signal, such as information about a transponder owner, such as status of consumables, medical status. The ECM system may have a reactive jammer that is used both for a reactive jamming function, and as the transponder monitor function.

A system for transmitting a wireless countermeasure signal to disrupt third party communications is disclosed that include an antenna configured to receive wireless signals and transmit wireless counter measure signals such that the wireless countermeasure signals are responsive to the received wireless signals. A receiver processes the received wireless signals to create processed received signal data while a spectrum control module subtracts known source signal data from the processed received signal data to generate unknown source signal data. The unknown source signal data is based on unknown wireless signals, such as enemy signals. A transmitter is configured to process the unknown source signal data to create countermeasure signals and transmit a wireless countermeasure signal over the first antenna or a second antenna to thereby interfere with the unknown wireless signals.

An accelerated superluminal polarization currents (ASPC) transceiver includes an ASPC transmitter including a plurality of ASPC radiator elements, the ASPC transmitter transmitting a radio signal that is focused in a target direction and scrambled in other directions; and a radio receiver, wherein the center of a pulse of the radio signal has a transit time t.sub.c from an end of the ASPC transmitter, at a first position x.sub.0, to a second position x along the ASPC transmitter given by the following equation: t.sub.c=[R.sup.2+x.sub.0.sup.2+2Rx.sub.0 cos .sub.0].sup.1/2[R.sup.2+x.sup.2+2Rx cos .sub.0].sup.1/2, where R is a target distance from the ASPC transmitter and .sub.0 is a target angle and $\frac{x+x_0}{t_c}>c.$

An apparatus, configured to communicate with other apparatuses in a wireless network and operating in a frequency-division duplexing mode, can be caused to refrain from transmitting during a number of subframes of a frame of a downlink frequency band prior to a detection of a radar transmission, can be caused to send a first signal, related to monitoring for the radar transmission, to a second apparatus, and can be caused to change the number of the subframes of the frame of the downlink frequency band in response to an event that can be an increase or a decrease in a load of the apparatus or the detection of the radar transmission. Optionally, placement of the subframes within the frame of the downlink frequency band can correspond to placement of subframes that are designated for an uplink communication within a frame configured in accordance with the Long-Term Evolution Time-Division Duplex standard.

A method and system of reliably detecting a reactive jamming attack and estimating the jammer's listening interval for exploitation by a communication system comprises channelizing one or more signals of interest (SOI), channelizing one or more signals of unknown origin (SUO), identifying frequency support patterns for the SOI and SUO using Bayes thresholds, comparing SOI and SUO detection map histories, and determining a percent match, where a match percentage above a specified minimum indicates a reactive attack. Edge detection can be used to enhance jammer support. Embodiments further detect reactive jammer adaptation to changes in the SOI's frequency support. Embodiments include detectors that are insensitive to jammer modulation and/or signal type. A jammer reaction delay and/or size and periodicity of receive window can be detected. Embodiments determine if a jammer is copying and retransmitting the SOI's waveform(s), and/or if the jammer is anticipatory.